| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a good image even by means of an AC light source and to detect a focus with high accuracy by changing a computing equation when the absolute value of the difference between an estimated monitoring signal level and a measured monitoring signal level is larger than a prescribed value. SOLUTION: A luminous flux from a subject is received by a photoelectric transducer away 1, an electric charge according to a quantity of incident light is accumulated, and a monitoring signal according to the accumulated amount of the electric charge is output to a monitoring-signal readout part 3 by a monitoring part 2. The readout part 3 reads out a monitoring signal level after the passage of a first time after the start of an accumulation operation, it estimates a monitoring signal level after the passage of a second longer time, and it reads out a measured monitoring signal level after the passage of the second time so as to be compared with an estimated monitoring signal level. When the absolute value of the difference between the estimated monitoring signal level and the measured monitoring signal level is larger than a prescribed value, a prescribed computing expression is changed. That is to say, an accumulated-time computing part 4 computes an accumulated time by a computing method which is different from an ordinary computing method.</p> |
